1. Field of the Invention
The present invention relates to a moving vehicle system. In particular, the present invention relates to position detection of a moving vehicle.
2. Description of the Related Art
In a known system, a detection head having a coil array including a plurality of coils is provided along a moving direction of a moving vehicle such as a transportation vehicle, a stacker crane, or a head of a working machine, and magnetic marks provided on the ground are detected to determine the position of the moving vehicle (See, for example, JP2002-337037A). With respect to such a system, the inventor studied to provide continuous segments where magnetic marks are arranged at a first pitch equal to the length of, e.g., a coil array to determine the position of the moving vehicle continuously, and discrete segments where magnetic marks are arranged at a pitch wider than the first pitch to determine the position of the moving vehicle only in segments including the magnetic marks. Further, magnetic sensors such as hall elements are provided at both ends of the detection head to detect the magnetic marks, and identify whether the moving vehicle is in the discrete segment or the continuous segment.
According to experiments of the inventor, in the case where the magnetic marks are present in the vicinity of a central portion of the coil array, the same position detection results are obtained regardless of the discrete segment or the continuous segment. It is because the coil array is influenced by only one magnetic mark. Further, a state in which the magnetic marks are provided at both ends of the coil array in the continuous segment and a state in which the magnetic mark is provided only at one end of the coil array in the discrete segment can be identified easily by the hall element. In this case, since no detection is performed in the discrete segments and detection is only performed in the continuous segments, no problems occur. In the case where a magnetic mark is present slightly inside one end of the coil array, another magnetic mark is present slightly outside the other end of the coil array in the continuous segment, and such a magnetic mark is not preset in the discrete segment. In this state, different detection results are obtained depending on the discrete segment or the continuous segment. However, the magnetic mark positioned slightly outside the coil array cannot be detected by the hall element, and whether the moving vehicle is in the discrete segment or the continuous segment cannot be identified. Therefore, for identification, another hall element needs to be provided outside in a direction in which the coil array is extended. However, provision of another hall element is not preferable since the length of the detection head is increased, and the number of components of the detection head is increased.